The demand for continued improvement in the efficiency of combustion turbine and combined cycle power plants has driven the designers of these systems to specify increasingly higher firing temperatures in the combustion portions of these systems. Although nickel and cobalt based superalloy materials are now used for components in the hot gas flow path, such as combustor transition pieces and turbine rotating and stationary blades, even these superalloy materials are not capable of surviving long term operation at temperatures sometimes exceeding 1,200 degrees C.
It is known in the art to coat a superalloy metal component with an insulating ceramic material to improve its ability to survive high operating temperatures; see for example U.S. Pat. No. 4,321,310 issued on Mar. 23, 1982, to Ulion et al. It is also known to coat the insulating ceramic material with an erosion resistant material to reduce its susceptibility to wear caused by the impact of particles carried within the hot gas flow path; see for example U.S. Pat. Nos. 5,683,825 issued on Nov. 4, 1997, to Bruce et al. and 5,562,998 issued on Oct. 8, 1996, to Strangman. Each of the above mentioned patents are incorporated by reference herein.
Much of the development in this field of technology has been driven by the aircraft engine industry, where turbine engines are required to operate at high temperatures, and are also subjected to frequent temperature transients as the power level of the engine is varied. A combustion turbine engine installed in a land-based power generating plant is also subjected to high operating temperatures and temperature transients, but it may also be required to operate at full power and at its highest temperatures for very long periods of time, such as for days or even weeks at a time. Prior art insulating systems are susceptible to degradation under such conditions at the elevated temperatures demanded in the most modern combustion turbine systems.
Accordingly, it is an object of this invention to provide a device which is capable of operating at temperatures in excess of 1,200 degrees C. for extended periods of time with reduced component degradation. It is a further object of this invention to provide a method of producing such a device that utilizes only commercially available materials processing steps.